1. Field of the Invention
The present invention relates to a connector holding structure for holding connectors on an electronic circuit board housed in a case.
2. Description of the Related Art
In an electronic circuit unit comprising an electronic circuit board, on which a connector is mounted, that is housed in a case, it is required that the connector is tightly fixed to the board, and mechanical and electrical connections between the connector and the electronic circuit board do not become unstable when a mating connector is inserted to and removed from the connector mounted on the electronic circuit board.
Further, in the manufacturing (assembly) process of the electronic circuit unit, it is desirable that the electronic circuit board on which a connector is mounted is easily inserted into a case, and the electronic circuit board is fixed at a predetermined position with high accuracy.
For this reason, as taught in Japanese Laid-Open Patent Application No. Hei 9(1997)-321462 (paragraphs 0010 and 0011, FIG. 1, etc.), a connector is fixed to an electronic circuit board by fastening with screws and soldering its lead terminals on the board. In addition, raised strips are integrally formed on the upper surface of the connector, and the raised strips are engaged between a pair of external force-receiving projections disposed on the internal surface of a case.
With this, when a mating connector is inserted to or removed from the connector mounted on the electronic circuit board, an excessive external force is not applied to the screwed and soldered portions of the connectors (stress is not generated), since, even if the connectors are twisted or shaken to be moved, the movement thereof is restricted by the raised strips coming into contact with the external force-receiving projections, whereby the mechanical and electrical connections between the connectors and the electronic circuit board are stabilized.
In the technique taught in Japanese Laid-Open Patent Application No. 2001-237557 (paragraphs 0032 to 0034, FIG. 2, etc.), flange-like projections 132 are protruded from surfaces 118a of connectors 118 (surfaces opposite to the surface facing an electronic circuit board 116) to be engaged with recesses 134 formed in a housing case main body 128; and rails 130 are formed on the inner wall of the housing case main body 128, for guiding the electronic circuit board 116, as shown in FIG. 11.
The connectors 118 are fixed to the electronic circuit board 116 by their soldered lead terminals; and after the electronic circuit board 116 has been inserted in the housing case main body 128 while being guided by the rails 130, and fixed at a predetermined position, the projections 132 engage the recesses 134. The electronic circuit board 116 with the connectors 118 is thereby easily inserted into the housing case main body 128, and the electronic circuit board 116 is fixed at a predetermined position, whereby the mechanical and electrical connections between the connectors 118 and the electronic circuit board 116 are stabilized.
In the technique disclosed in '462, since it is configured such that the connectors are fixed to the electronic circuit board by screws, a relatively high level of yield strength against twist or shake (twist/shake yield strength) can be obtained when inserting the mating connectors to the connectors on the electronic circuit board or removing therefrom. However, this requires a screwing process and results in increase in labor cost and the number of components.
Further, in the technique disclosed in '557, since it is configured such that the lead terminals of the connectors 118 are soldered to the electronic circuit board 116, the process to fix the connector by screwing is not necessary. However, as shown in FIG. 11, the projections 132 are to be protruded from the side walls 118a of the connectors 118 in the insertion direction, and recesses 134 are to be formed at locations corresponding to the projections 132 on the housing case main body 128, i.e., the connections (boundary lines) of the connectors 118 and projections 132 and the connections of the housing case main body 128 and the recesses 134 are formed so as to be orthogonal to the insertion direction.
For this reason, the projections 132 should have a predetermined length (indicated by “L1” in FIG. 12) so as not to slip out from the recesses 134 if the twisting/shaking force is applied when mating connectors are inserted or removed, particularly when downward twisting/shaking force in the insertion direction is applied to the projections 132. Therefore, when the mating connectors are inserted to or removed from the connectors 118 and external force due to twist or shake in the direction of the arrow A of FIG. 12 is exerted on the connector 118, the resulting moment intensively acts on the base portions 132a of the projections 132, and the projections 132 deform in the manner shown by a phantom line in the figure.
As a result, the projections 132 are occasionally damaged and the connections between the connectors and the electronic circuit board are liable to be unstable due to an excessive external force (a stress) acting on the soldered portion of the lead terminals of the connectors 118.
In this case, it will be sufficient if resistance against twist or shake is strengthened, i.e., if the thickness t1 of the projections 132 is increased so as to prevent the projections 132 from deforming, but it brings a drawback that the thickness (height) t of the entire housing case is increased with increasing thickness of the projections 132.